In manufacturing semiconductor devices, various processes are used to heat treat an object to be processed, for example, a semiconductor wafer. The heat treatment includes oxidation, diffusion, chemical vapor deposition (CVD), and annealing. For example, a vertical heat treatment apparatus may be used to heat treat a plurality of wafers at one time.
In general, the vertical heat treatment apparatus includes a reaction tube provided in a heat treatment furnace and a lid installed to be vertically movable to open and close a furnace opening of the reaction tube. The furnace opening of the reaction tube is sealed by the lid.
In general, the reaction tube is made of quartz, and the lid is made of metal. An O-ring that protrudes from the lid is brought into contact with the reaction tube. When the quartz reaction tube is sealed by the metal lid, a gap is defined between the quartz reaction tube and the metal lid.
In another arrangement, a metal outer lid part supports an inner lid. The inner lid includes a quartz inner lid part positioned near a reaction tube. An O-ring is located between the quartz inner lid part and the reaction tube which can be made of quartz. When the reaction tube is sealed by the quartz inner lid part, the reaction tube is brought into contact with the lid.
In the vertical heat treatment apparatus, when the furnace opening of the reaction tube is sealed by the lid as described above, a bottom flange of the reaction tube is sealed by the lid.
However, since among the reaction tube and the lid, at least the reaction tube is made of quartz, when the lid is brought into contact with the bottom flange of the reaction tube, quartz particles may be generated as they are used more frequently. Thus, such quartz particles may sometimes be introduced into the reaction tube.
In addition, if there is a gap between the reaction tube and the lid to prevent the reaction tube from being brought into contact with the lid, a corrosive gas such as a cleaning gas may be introduced through the gap, thereby corroding other metal parts. Further, even though an inert gas supply unit is provided to prevent the corrosive gas from being introduced through the gap, when a sufficient gap is not formed because the amount of deformation of a sealing member is mis-calculated, a reverse diffusion of the corrosive gas occurs, thus corroding the other metal parts.